Subpopulation Differences in Intervention Efficacy for College Drinkers. Despite prevention efforts, college binge drinking continues to account for a myriad of negative personal and social alcohol-related consequences. Brief motivational interventions (BMIs) have proved efficacious in reducing college alcohol consumption;however, averaging across people, reported intervention effects tend to be small and short-lived. It is often of more interest to understand who responds to an intervention rather than determine the average effect across different subpopulations. Instead of characterizing intervention efficacy for a "typical" college drinker, the purpose of this research is to characterize intervention effects across different subpopulations, or types, of drinkers. Moderation analyses test hypothesized factors that may influence intervention efficacy. In contrast to traditional moderation analyses, growth mixture modeling (GMM) empirically explores the data to identify homogenous longitudinal patterns in alcohol consumption without need of pre-identified predictors. Using GMMs, past research has identified up to five types of drinkers regarding naturally-occurring trajectories of alcohol consumption over time;however, the proposed project takes a novel approach by exploring drinking patterns following intervention. The proposed project includes secondary data analysis of 3 randomized clinical trials with a combined total of 1,384 college-student drinkers (509 volunteers, 875 mandated as a result of alcohol violations), whose drinking behaviors were assessed at baseline, and at 1, 6, and 12 months post-intervention. Participants were randomized into a BMI (n = 602), 1 of 2 computerized interventions (Alcohol 101, n = 271;Alcohol EDU, n = 167), or a no-intervention control condition (n = 344). The four specific aims are a) to identify how many different subpopulations of college drinkers exist regarding short- and long-term response to an alcohol BMI;b) to characterize BMI efficacy relative to computerized intervention and a control for each type of drinker;c) to use demographic and psychological explanatory variables to characterize each drinker subpopulation;and d) ascertain how drinker subpopulations relate to high-risk alcohol consequences. Discontinuous GMMs will be used to ascertain how different types of drinkers uniquely respond following intervention from baseline to 1-month (short-term effect) and from 1-month to 12- months (long-term effect), as well as to identify relevant psychological predictors of drinker subpopulations among both sanctioned individuals and volunteers. Results of this research can be used to understand who is most receptive to BMI intervention, to guide screening efforts to reliably detect high-risk individuals, and to use the information about the most resistant subpopulation(s) to inform future intervention development. PUBLIC HEALTH RELEVANCE: Subpopulation Differences in Intervention Efficacy for College Drinkers The proposed research will use innovative and advanced statistical modeling to identify subpopulation characteristics of individuals who respond and do not respond to interventions designed to reduce alcohol consumption among college drinkers. The results of this research can be used to understand who is most receptive to brief motivational intervention, to guide screening efforts to reliably detect high-risk individuals, and to use the information about the most resistant subpopulation(s) to inform future intervention development. Improved screening and intervention methods are critical to reducing personal and social alcohol-related consequences among college populations.